Patients with limb amputations could be trained to overcome phantom limb pain, say German researchers.

Writing in this week's issue of The Lancet, Herta Flor and colleagues from the Central Institute of Mental Health, Mannheim, describe an experiment in which sensory discrimination training was used to reverse phantom limb pain.

Phantom limb pain often happens as a result of the amputation of a body part but researchers don't know what causes this disabling condition - which affects up to 80% of amputees - and few effective treatments are available.

Flor and colleagues compared five patients with arm amputation with a control group of five other amputee patients who received standard medical treatment, which included pain killers, nerve stimulation, or physical therapy.

In the training group, eight electrodes were attached to the arm stump. Patients participated in ten daily 90 minute sessions over two weeks of feedback-guided sensory training, in which they had to discriminate the frequency or location of high intensity non-painful electric stimuli applied randomly through the electrodes.

Patients in the control group participated in a psychophysiological assessment in the course of the two weeks. Neurological, psychometric, psychophysical, and psychophysiological testing took place before, immediately after, and three months after the treatment in both groups.

Patients given training showed a significant improvement in the ability to discriminate both the location and the frequency of the stimulation. At the same time, the phantom limb pain in all patients decreased during and after the training whereas there were no significant changes in the controls.

Changes in the brain previously associated with limb amputation were also found to occur less often in patients given sensory training.

Flor suggests that such changes in the brain and the ability to discriminate are both interrelated and involved in the reduction in phantom limb pain.